The coefficient is 12a because it has a variable (a).
Answer:
Option C is the correct answer
Step-by-step explanation:
is supplementary to 
First you have to make the denominator the same for each fraction: /4 -> /12, /3 -> /12
Second multiply your numerator as well, in this case by 3: 6 * 3 = 18, 18/12, x/12
I think you've got it from here.